Cellulose biomass is said to be the most abundant resource in natural resources, and thus an efficient application of cellulase systems which decompose the cellulose biomass is desired in various fields. In this development process, various cellulases were purified and characterized, and further, various cellulase genes were cloned, and classified into families by analyzing the sequence homology (see non-patent reference 1).
In another aspect, cellulases are utilized, based on their properties, in various industrial fields, particularly the field of fabric processing. For example, treatment with cellulase is carried out to improve the touch and/or appearance of cellulose-containing fabric, or for a “biowash”, which imparts a “stonewash” appearance to colored cellulose-containing fabric, thereby providing the fabric with localized color variations. Further, in the process for manufacturing lyocell, cellulase is used for removing the fuzz generated in the process from the fabric surface. In this connection, lyocell is a regenerated cellulose fabric derived from wood pulp, and has recently attracted attention for its properties (such as high strength or water absorption) and as a production process that causes less environmental pollution.
Hitherto, it has been considered that cellulase decomposes cellulose by the collaborative effect of plural enzymes, i.e., synergy effect. The cellulase group consisting of plural enzymes contains enzymes having properties inappropriate for the field of fabric processing (such as an enzyme which lowers a fiber strength). Therefore, an attempt to separate enzyme components appropriate for fabric processing from the cellulase group, and to produce the enzyme components, has been carried out by utilizing protein separation techniques and/or genetic engineering techniques. Particularly, cellulases derived from microorganisms belonging to filamentous fungi such as genus Trichoderma or genus Humicola have been subjected to serious study. For example, as cellulase components, CBH I, EG V (see patent reference 1), NCE2, NCE4, and NCE5 in genus Humicola, and CBH I, CBH II, EG II, and EG III in genus Trichoderma were isolated, and thus, cellulase preparations containing as the major components one or more specific cellulase components appropriate for each purpose can be produced by preparing overexpressed enzymes or monocomponent enzymes using genetic engineering techniques. Further, it is clarified that cellulases belonging to family 45, such as NCE4 (see patent reference 2), NCE5 (see patent reference 3), RCE1 (see patent reference 4), or STCE1 (see International Application No. PCT/JP2004/15733), are very useful in the above fields.
In still another aspect, when cellulases are used as a detergent for clothing, not only quantitative improvement of cellulase components used but also qualitative one is desired. More particularly, a detergent for clothing contains various surfactants, and a solution obtained by solubilizing the detergent for clothing in water is alkaline (pH10 to pH11). Therefore, it is necessary that cellulases contained in a detergent for clothing should be resistant to various surfactants under alkaline conditions. As a report in which a reduction in an activity in the presence of a surfactant is suppressed, it was reported by Otzen, D. E. et al. that when a mutation was introduced into the internal amino acid sequence of Ce145 derived from Humicola insolens, the activity thereof at pH7 in the presence of linear alkyl benzene sulfonate (LAS) was approximately 3.3 times higher than that of the wild-type (see non-patent reference 2). However, it is found that the suppression of a reduction in the activity in the presence of the surfactant, provided by the mutation, is limited to Ce145 or homologous proteins thereof, and that is not applicable to endoglucanases belonging to family 45 having a low homology with Ce145.    (patent reference 1) International Publication WO91/17243    (patent reference 2) International Publication WO98/03667    (patent reference 3) International Publication WO01/90375    (patent reference 4) International Publication WO00/24879    (non-patent reference 1) Henrissat B., Bairoch A. Updating the sequence-based classification of glycosyl hydrolases. Biochem. J. 316:695-696 (1996)    (non-patent reference 2) Daniel E. Otzen, Lars Christiansen, Martin Schulein. A comparative study of the unfolding of the endoglucanase Ce145 from Humicola insolens in denaturant and surfactant. Protein Sci. 8:1878-1887 (1999)